6 markers cost $9.18. Which equation would help determine the cost of 10 markers?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 6 markers. We want to know the cost of 10 markers. We can write the numbers of markers as a proportion: $\dfrac{6}{10}$ We know 6 markers costs $9.18. We can let $x$ represent the unknown cost of 10 markers. The proportion of these costs can be expressed as: $\dfrac{\$9.18}{x}$ The cost changes along with the number of markers purchased, and so the two proportions are equivalent. $\dfrac{6}{10} = \dfrac{\$9.18}{x}$